I'm pretty sure this is relatively new. There's no more separate enrolments for OS X and iOS anymore, it's just developing for Apple (OS X, iOS, WatchOS). And as another note, it was just a few days ago when I noticed my dev account had expired and the renewal was AUD$149. Now it's just AUD$99 for everything. With Apple, at least, I could've asked for a refund of the difference and gotten it.